Thor-Ablestar

American expendable launch system

The launch of a Thor-Ablestar 2 with a Transit satellite.

Function| Orbital carrier rocket
Manufacturer| Douglas / Aerojet
Country of origin| United States
Size
Height| 29 metres (95 ft)
Diameter| 2.44 metres (8 ft 0 in)
Mass| 53,000 kilograms (117,000 lb)
Stages| 2
Capacity
Payload to 1100km LEO
Mass| 150 kilograms (330 lb)
Associated rockets
Family| Thor
Comparable| Delta
Launch history
Launch sites| LC-17, Canaveral
LC-75-1, Arguello
Total launches| 19
Success(es)| 12
Failure(s)| 5
Partial failure(s)| 2
First flight| 13 April 1960
Last flight| 13 August 1965
First stage – Thor
Powered by| 1 MB-3-1
Maximum thrust| 760.64 kilonewtons (171,000 lbf)
Specific impulse| 285 sec
Burn time| 164 seconds
Propellant| RP-1/LOX
Second stage – Ablestar
Powered by| 1 AJ10-104, AJ10-104D
Maximum thrust| 36.02 kilonewtons (8,100 lbf)
Specific impulse| 280 sec
Burn time| 296 seconds
Propellant| HNO3/UDMH

[edit on Wikidata]

The Thor-Ablestar, or Thor-Able-Star, also known as Thor-Epsilon [1] was an early American expendable launch system consisting of a PGM-17 Thor missile, with an Ablestar upper stage. It was a member of the Thor family of rockets, and was derived from the Thor-Able.

The improved Able-Star version was used as the upper stage of the Thor-Ablestar two stage launcher. The Able-Star second stage was an enlarged version of the Able rocket stage using AJ10-104 or AJ10-104D engines, which gave the Thor-Ablestar a greater payload capacity compared to the earlier Thor-Able.[2] It also incorporated restart capabilities, allowing a multiple-burn trajectory to be flown, further increasing payload, or allowing the rocket to reach different orbits. It was the first rocket to be developed with such a capability and development of the stage took a mere eight months.[3]

Two versions were built; the Thor-Ablestar 1, with a DM-21 Thor and an AJ-10-104 second stage engine, and the Thor-Ablestar 2, which had a DSV-2A Thor first stage, and an uprated AJ-10-104D engine on the second stage.[1] Thor-Ablestar 1 launches occurred from LC-17 at Cape Canaveral, and Thor-Ablestar 2 rockets were launched from LC-75-1 at Vandenberg Space Force Base (now designated SLC-2).

## Launches

[edit]

Nineteen Thor-Ablestar were launched between 1960 and 1965, of which four failed, and a fifth resulted in a partial failure, as only one of two payloads separated from the upper stage.[4]

The first failure was the launch of Courier 1A, an experimental communications satellite, on 19 August 1960 when the first stage shut down 30 seconds earlier than planned and was destroyed by the Range Safety Officer.

On 30 November, another launch involving a Transit satellite failed in practically identical fashion. This episode nearly created an international incident as parts of the Thor landed in Cuba. War was threatened. Cuban leader Fidel Castro subsequently sold off the Thor's engine to the Soviets and the Chinese received its thrust vectors, which ended up proving valuable to the latter's development of a ballistic missile capability. To prevent this from happening again, future Thor Ablestar launches had their flight paths modified to avoid passing over Cuba.

The launch of a Transit satellite on 22 February 1961 was successful, but its companion Lofti satellite failed to separate from the second stage.

On 29 June 1961, a Thor-Ablestar successfully inserted a Transit-4A into orbit, but two hours later the Ablestar exploded for unknown reasons into hundreds of pieces, which remained in orbit. This is the first known artificial object to break up unintentionally in space.[5]

The third launch failure occurred on 24 January 1962 when the second stage produced insufficient thrust to achieve orbital velocity for several piggybacked satellites.[6] The fourth and final failure was the launch of an Anna geodetic satellite on 10 May 1962 when the second stage completely failed to ignite.

This section is transcluded from List of Thor-Ablestar launches. (edit | history)

Date/Time

(UTC)

| S/N | Version  | Launch Site  | Payload  | Function  | Outcome  | Photo

|
|
|
|
|
|
|

1960-04-13

12:02:36

| Thor 257

Ablestar 002

| Thor-DM21 Able-Star  | CCAFS LC-17B | Transit 1B | Navigation  | Success, maiden flight of Thor-Ablestar  |
1960-06-22

05:54

| Thor 281

Ablestar 003

| Thor-DM21 Able-Star  | CCAFS LC-17B  | Transit 2A, GRAB-1 (Solrad 1)  | Navigation, ELINT  | Success  |
1960-08-18

19:58

| Thor 262

Ablestar 004

| Thor-DM21 Able-Star  | CCAFS LC-17B  | Courier 1A | Communications  | Failure (Premature first stage cutoff. RSO T+150 seconds.)  |
1960-10-04

17:50

| Thor 293

Ablestar 005

| Thor-DM21 Able-Star  | CCAFS LC-17B  | Courier 1B | Communications  | Success  |
1960-11-30

19:50

| Thor 283

Ablestar 006

| Thor-DM21 Able-Star  | CCAFS LC-17B  | Transit 3A, GRAB-2 (Solrad-2)  | Navigation, ELINT  | Failure (Premature Thor cutoff. RSO. Debris fell in Cuba.)  |
1961-02-22

03:45

| Thor 313

Ablestar 007

| Thor-DM21 Able-Star  | CCAFS LC-17B  | Transit 3B, LOFTI-1 | Navigation, Technology  | Success  |
1961-06-29

04:22

| Thor 315

Ablestar 008

| Thor-DM21 Able-Star  | CCAFS LC-17B  | Transit 4A, Injun 1, GRAB-3 (Solrad 3)  | Navigation, Ionospheric, ELINT  | Success  |
1961-11-15

22:26

| Thor 305

Ablestar 009

| Thor-DM21 Able-Star  | CCAFS LC-17B  | Transit 4B, TRAAC | Navigation  | Success, Transit Research and Attitude Control  |
1962-01-24

09:30

| Thor 311

Ablestar 010

| Thor-DM21 Able-Star  | CCAFS LC-17B  | LOFTI-2, SECOR, GRAB-4 (Solrad 4), Injun 2, SURCAL 1 | Technology, Geodesy, ELINT, Ionospheric, Calibration  | Failure (second stage insufficient thrust)  |
1962-05-10

12:06

| Thor 314

Ablestar 011

| Thor-DM21 Able-Star  | CCAFS LC-17B  | ANNA 1A | Geodesy  | Failure (second stage failed to ignite)  |
1962-10-31

08:08

| Thor 319

Ablestar 012

| Thor-DM21 Able-Star  | CCAFS LC-17A | ANNA 1B | Geodesy  | Success, final flight of Thor DM-21 Ablestar  |
1963-09-28  | Thor 375  | Thor-DSV2A Able-Star  | VAFB LC-75-1-1 | Transit 5BN-1 / Transit 5E-1  | Navigation  | Success  |
1963-05-12  | Thor 385  | Thor-DSV2A Able-Star  | VAFB LC-75-1-1  | Transit 5BN-2 / Transit 5E-3  | Navigation  | Success  |
1964-04-21

18:50

| Thor 379

Ablestar 014

| Thor-DSV2A Able-Star  | VAFB LC-75-1-1  | Transit 5BN-3, Transit 5E-4 | Navigation  | Failure  |
1964-10-06

17:04:21

| Thor 423

Ablestar 016

| Thor-DSV2A Able-Star  | VAFB LC-75-1-2  | OPS 5796 (Transit O-1),

Dragsphere 1, Dragsphere 2

| Navigation  | Success  |
1964-12-13

00:08:10

| Thor 427

Ablestar 017

| Thor-DSV2A Able-Star  | VAFB LC-75-1-2  | OPS 6582 (Transit O-2) (Transit 5B-5), Transit 5E-5 | Navigation  | Success  |
1965-03-11

13:39

| Thor 440

Ablestar 018

| Thor-DSV2A Able-Star  | VAFB LC-75-1-1  | OPS 7087 (Transit O-3), SECOR 2 | Navigation, Geodesy  | Success  |
1965-06-24

22:35

| Thor 447

Ablestar 019

| Thor-DSV2A Able-Star  | VAFB LC-75-1-1  | OPS 8480 (Transit O-4)  | Navigation  | Success  |
1965-08-13

22:11

| Thor 455

Ablestar 020

| Thor-DSV2A Able-Star  | VAFB LC-75-1-1  | OPS 8464 (Transit O-5), Dodecapole 2, Tempsat 1, Surcal 5, Long Rod 1, Calsphere 2 | Navigation, Calibration  | Success, final flight of Thor-Ablestar  |

## See also

[edit]

* List of Thor and Delta launches (1960–1969)

## References

[edit]

1. ^ a b Krebs, Gunter. "Thor Able-Star". Gunter's Space Page. Retrieved 30 November 2008.
2. ^ "Able-Star". www.astronautix.com. Retrieved 27 July 2025.
3. ^ Wade, Mark. "Delta". Encyclopedia Astronautica. Archived from the original on 24 July 2008. Retrieved 30 November 2008.
4. ^ Wade, Mark. "Delta". Encyclopedia Astronautica. Archived from the original on 17 August 2013. Retrieved 30 November 2008.
5. ^ Orbital Debris: A Chronology (PDF). NASA JSC. January 1999. p. 18\. Archived from the original (PDF) on 1 September 2000. Retrieved 13 February 2016. "Two hours after separating from the U.S. Transit 4-A satellite, its Able Star upper stage becomes the first known artificial object to break up unintentionally in space. The cause of the explosion is unknown. The event produces at least 294 trackable pieces, more than tripling the number of known satellites of Earth."
6. ^ "A-Okay So Far: Glenn, Atlas Ready". The Gazette. Montreal, QC. Associated Press (AP). 25 January 1962. p. 1. Retrieved 29 December 2015.

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* This template lists historical, current, and future space rockets that at least once attempted (but not necessarily succeeded in) an orbital launch or that are planned to attempt such a launch in the future
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Thor and Delta rockets

* PGM-17 Thor
* Thor family
* Delta family

Rockets|

| Thor|

* Thor
* Thor-Able
* Thor-Ablestar
* Thor-Agena
* Thor-Burner
* Thor-Delta
* Thor DSV-2
* Thor DSV-2U
* Thorad-Agena

|

Delta|

| Alphabetical|

* Delta A
* Delta B
* Delta C
* Delta D
* Delta E
* Delta F
* Delta G
* Delta J
* Delta L
* Delta M
* Delta N

|

Numerical|

* Delta 0100
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* Delta 9000

Modern|

* Delta II
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Export|

* N-I
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Launch sites|

| Canaveral|

* (S)LC-17
* LC-18B
* SLC-37B

|

Johnston|

* LE-1
* LE-2

Tanegashima|

* Osaki

Vandenberg|

* SLC-1
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* SLC-10

Bases|

* Bardney
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Components|

| Boosters|

* Castor-1
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* Castor-4A
* CBC
* GEM-40
* GEM-46
* GEM-60

|

First stages|

* Common Booster Core

Upper Stages|

| Delta|

* Delta-A
* Delta-D
* Delta-E
* Delta-F
* Delta-K
* Delta-P
* DCSS

|

Other|

* Able
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* UM-129

Engines|

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Manufacturers|

| Rocket|

* Douglas
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* United Launch Alliance

|

Engines|

* Aerojet
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Launches|

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